High capacity electrochemically active materials are very desirable for battery applications. However, these materials exhibit substantial volume changes during battery cycling, such as swelling during lithiation and contracting during delithiation. For example, silicon swells as much as 400% during lithiation to its theoretical capacity of about 4200 mAh/g or Li4.4Si structure. Volume changes of this magnitude cause pulverization of active materials structures, losses of electrical connections, and capacity fading.
Providing high capacity materials as nanostructures can address some of these issues. Small dimensions of nanostructures cause less overall dimensional changes, which may be less mechanically destructive. However, integrating nanostructures into commercially-scaled battery electrodes layers has been challenging difficult. For example, nanofilms deposited on conventional flat substrates, such as metal foils, generally do not provide adequate loading. Furthermore, many processes proposed for fabricating nanostructures are slow and often involve expensive materials. For example, etching silicon nanowires from bulk particles requires silver catalysts and expensive etching solution. Growing long crystalline silicon structures can also be a relative slow process and may involve expensive catalysts, such as gold.